Synthesis and characterization of a Schiff base derived from 2-aminobenzylamine and its Cu(II) complex: Electropolymerization of the complex on a platinum electrode

Article abstract of DOI:10.1080/00958972.2010.496852

A precursor (H₃A) was synthesized by the mono condensation of 2-aminobenzylamine with salicylaldehyde and then a tetradentade Schiff-base ligand (H₂L) prepared by using H₃A and 3-methoxysalicylaldehyde. The copper(II) complex of this new ligand was prepared and characterized by elemental analysis, electronic absorption, Fourier transform infrared (FT-IR), and magnetic susceptibility. For the ligand, ¹H- and ¹³C-NMR and liquid chromatography mass spectrometry (LC-MS) spectra were obtained. The tetradentate ligand is coordinated to Cu(II) through the phenolic oxygen and azomethine nitrogen. The use of this metal complex in the preparation of a modified electrode is also described. CuL was electropolymerized on a platinum electrode surface in a 0.1 mol dm^-3 solution of lithium perchlorate in acetonitrile by cyclic voltammetry between 0 and 1.6 V versus Ag/Ag+. Electrochemical properties of the electroactive polymeric film have been investigated and a surface confined polymerization mechanism was proposed.

Full text of DOI:10.1080/00958972.2010.496852

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Synthesis and characterization
of a Schiff base derived from 2-
aminobenzylamine and its Cu(II)
complex: electropolymerization of the
complex on a platinum electrode
Cahıt Demetgül a , Dıdem Deletıoğlu a , Fılız Karaca b , Süleyman
Yalçinkaya a , Mahır Tımur a & Selahattın Serın b
a Department of Chemistry, Faculty of Science and Letters,
Mustafa Kemal University, Hatay 31040, Turkey
b Department of Chemistry, Faculty of Science and Letters,
Çukurova University, Adana 01330, Turkey
Published online: 25 Jun 2010.
To cite this article: Cahıt Demetgül , Dıdem Deletıoğlu , Fılız Karaca , Süleyman Yalçinkaya , Mahır
Tımur & Selahattın Serın (2010): Synthesis and characterization of a Schiff base derived from 2-
aminobenzylamine and its Cu(II) complex: electropolymerization of the complex on a platinum
electrode, Journal of Coordination Chemistry, 63:12, 2181-2191
To link to this article: http://dx.doi.org/10.1080/00958972.2010.496852
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Journal of Coordination Chemistry
Vol. 63, No. 12, 20 June 2010, 2181–2191
Synthesis and characterization of a Schiff base derived from
2-aminobenzylamine and its Cu(II) complex:
electropolymerization of the complex on a platinum electrode
_
_
_
_ _
˘
¨
CAHIT DEMETGUL*y, DIDEM DELETIOGLUy, FILIZ KARACAz,
_
_
¨
SULEYMAN YALC
¸
INKAYAy, MAHIR TIMURy and
_ _
SELAHATTIN SERINz
yDepartment of Chemistry, Faculty of Science and Letters, Mustafa Kemal University,
Hatay 31040, Turkey
zDepartment of Chemistry, Faculty of Science and Letters, C
¸ ukurova University,
Adana 01330, Turkey
(Received 30 December 2009; in final form 23 March 2010)
A precursor (H3A) was synthesized by the mono condensation of 2-aminobenzylamine with
salicylaldehyde and then a tetradentade Schiff-base ligand (H2L) prepared by using H3A and
3-methoxysalicylaldehyde. The copper(II) complex of this new ligand was prepared and
characterized by elemental analysis, electronic absorption, Fourier transform infrared (FT-IR),
and magnetic susceptibility. For the ligand, 1H- and 13C-NMR and liquid chromatography
mass spectrometry (LC–MS) spectra were obtained. The tetradentate ligand is coordinated to
Cu(II) through the phenolic oxygen and azomethine nitrogen. The use of this metal complex
in the preparation of a modified electrode is also described. CuL was electropolymerized on
a platinum electrode surface in a 0.1 mol dmꢀ3 solution of lithium perchlorate in acetonitrile by
cyclic voltammetry between 0 and 1.6 V versus Ag/Agþ. Electrochemical properties of the
electroactive polymeric film have been investigated and a surface confined polymerization
mechanism was proposed.
Keywords: 2-Aminobenzylamine; Schiff base; Copper(II) complex; Electropolymerization;
Modified electrode
1. Introduction
Schiff bases derived from substituted salicylaldehydes and various aromatic amines are
common polydentate ligands in coordination chemistry, coordinating in deprotonated
or neutral forms [1, 2]. Transition metal(II) complexes derived from tetradentate Schiff
bases form stable compounds where the coordination takes place through the N2O2
donor set [3]. Complexes of Schiff bases containing O, N donors are of particular
interest [4] because of unusual configuration, structural lability, and sensitivity
to molecular environments [5]. Thus, Schiff-base complexes have been among the
most widely studied coordination compounds and are becoming increasingly important
*Corresponding author. Email: cdemetgul@hotmail.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ꢀ 2010 Taylor & Francis
DOI: 10.1080/00958972.2010.496852

2182
C. Demetgul et al.
¨
as analytical, biochemical, and antimicrobial reagents [6]. These compounds also find
catalytic applications ranging from asymmetric epoxidation [7], solid phase extraction
of metal ions [8], polymerization [9, 10], and for the preparation of ion selective
electrodes [11, 12].
Conducting polymers containing complexed transition metals are increasing [13],
especially because metal centers can be electrically connected via the polymer skeleton.
Preparation and characterization of metal salen-based electroactive polymers is an
active field due to their potential application as electrocatalysts, chemical sensors,
or optical devices. The incorporation of metal salen complexes into a polymeric system
offers some advantages in the possibility of thickness control, good membrane-forming
properties, amperometric measurements in aqueous media, and easy preparation of
the modified electrodes. There has been interest in chemically modified solid electrodes,
including those coated with anodically polymerized films of metal salen complexes
[14–17]. A recent study is the electrochemical preparation involving electrocatalytic
oxidation of sulfite on a platinum electrode with Cu(II)-salen polymer film [18].
We report the synthesis and characterization of a Schiff base from 2-aminobenzy-
lamine and its Cu(II) complex. The characterization was done by elemental analysis,
atomic absorption spectroscopy (AAS), liquid chromatography mass spectrometry
1
(LC–MS), Fourier transform infrared (FT-IR), ultraviolet visible (UV-Vis), H-NMR,
and 13C-NMR. The new Cu(II) complex was electropolymerized on platinum electrode
in a 0.1 mol dmꢀ3 solution of lithium perchlorate in acetonitrile by cyclic voltammetry
(CV) between 0 and 1.6 V versus Ag/Agþ.
2. Experimental
2.1. Instrumentation
All melting points were measured in sealed tubes using an electrothermal digital melting
point apparatus (Gallenkamp) and are uncorrected. Vibrational properties were studied
on a Perkin Elmer RX-1 FT-IR spectrometer from 4000 to 400 cmꢀ1 as KBr pellets.
The ultraviolet visible (UV-Vis) spectra were measured using a Perkin Elmer Lambda
25 UV-Vis spectrometer. 1H-NMR and 13C-NMR spectra of the Schiff base were
recorded at 25ꢁC on a resolution Fourier transform Bruker Biospin 300 MHz
spectrometer with tetramethylsilane as an internal standard. Chemical shifts were
reported in ppm relative to the solvent peak. Elemental microanalysis of C, H, and N
were performed with a LECO-CHNS-932 elemental analyser. Mass spectra were
recorded on a LC–MS-APIES AGILENT model 1100 MSD. Metal analysis was carried
out by AAS Perkin Elmer 3100 in solutions prepared by decomposing the complex in
aqua regia and then digesting in concentrated HCl. Magnetic measurement was carried
out with a Sherwood magnetic susceptibility balance (Model MK1) with CuSO4 Á 5H2O
as the calibrant.
All electrochemical studies were conducted at ambient conditions using a CHI 606
model electrochemical analyzer under computer control. The electrochemical cell
consisted of a standard three-electrode system; the counter and working electrodes were
a platinum sheet (with 2 cm2 surface area), and Ag/Agþ electrode was used as the
reference. Photographs of non-modified platinum and [CuL] polymer film modified
platinum electrodes were taken by a Sony digital camera.

Schiff-base electropolymer
2183
2.2. Materials
All starting compounds and solvents for synthesis were purchased from Fluka and
Merck. Solvents and reagents were of technical grade and were purified and dried
by distillation from appropriate desiccant when necessary. Concentration of solutions
after reactions and extractions were achieved using a rotary evaporator at reduced
pressure. Analytical and preparative thin layer chromatography (TLC) was performed
on silica gel HF-254 (Merck).
2.3. Synthesis of Schiff bases H3A and H2L
The precursor (H3A) was prepared according to the modified method described [19, 20]
by mono condensation of 2-aminobenzylamine with salicylaldehyde. A two-neck flask
equipped with magnetic stirrer, water condenser, and dropping funnel was charged with
a dilute solution of the 2-aminobenzylamine (30 mmol) in absolute ethanol (80 cm3).
The solution was cooled (ꢀ5ꢁC) with stirring, and ethanol solution (40 cm3) of
salicylaldehyde (25 mmol) was added dropwise over 30 min. The reaction mixture was
stirred for an additional 5 h at the same temperature. The resulting solution was
evaporated under vacuum to remove the solvent and excess unreacted aminobenzyl-
amine was extracted by benzene. The structure of H3A is given in figure 1.
H3A: Color: yellow, yield (70%), m.p. 116ꢁC. LC–MS (m/e): 226.25 g molꢀ1
(C14H14N2O) Found % (Calcd %) C: 74.34 (74.32), H: 6.20 (6.24), N: 12.39 (12.38).
.
FT-IR (KBr, cmꢀ1): 3463 ꢀ(OH), 3374–3221 ꢀ(NH2), 3024 ꢀ(Ar–H), 2878 ꢀ(CH2), 1630
1
ꢀ(CH¼N), and 1278 ꢀ(C–OH). UV-Vis (ꢁmax, nm, EtOH): 319, 273. H-NMR (CDCl3
as solvent, ꢂ in ppm): 13.15 (s, OH), 8.60 (CH¼N), 7.40–6.50 (Ar–H), 4.75 (CH2),
and 3.70 (NH2). 13C-NMR (CDCl3 as solvent, ꢂ in ppm): 163 (CH¼N), 161 (C–OH),
145 (C–NH2), 133–115 (Ar), and 59 (–CH2–).
H2L was synthesized according to the literature [21]. An ethanol solution (20 cm3)
of 3-methoxysalicylaldehyde (20 mmol) and 50 cm3 precursor (H3A) (20 mmol) were
mixed and refluxed for 4 h. Then, the reaction mixture was cooled to room temperature
and allowed to precipitate. After filtering, the residue was washed several times with
ethanol and dried in vacuum. The ligand has a honey-like form. The composition of
1
the ligand was confirmed by elemental analysis, FT-IR, UV-Vis, LC–MS, H-NMR,
and 13C-NMR spectra. The structure of H2L is given in figure 2.
H2L: Yield (85%), color: orange, LC–MS (m/e): 360.18 g molꢀ1. (C22H20N2O3) Found
% (Calcd %): C: 73.32 (73.30), H: 5.59 (5.63), N: 7.77 (7.75). FT-IR (KBr, cmꢀ1): 3447
ꢀ(OH), 3056 ꢀ(Ar–H), 2834 ꢀ(CH2), 1630; 1615 ꢀ(CH¼N) and 1275; 1254 ꢀ(C–OH).
NH2
N
EtOH
O
H2N
–5°C, 5h
+
OH
OH
H2N
(H3A)
Figure 1. Synthesis of H3A.

2184
C. Demetgul et al.
¨
11
10
9
12
13
O
N
8
EtOH
14
+
H2N
15
16
Reflux, 4 h
7
N
N
OH
22
20
HO
5
6
1
OCH3
21
(H3A)
4
HO
OH
17
2
3
18
(H2L)
H3CO
19
Figure 2. Synthesis of H2L.
N
N
Cu2+
O
O
H3CO
Figure 3. The proposed structure of [CuL].
1
UV-Vis (ꢁmax, nm, EtOH): 320, 270. H-NMR (CDCl3 as solvent, ꢂ in ppm): 13.60–
13.00 (br, 2H, OH), 8.90 (s, 1H, CH¼N–CH2–); 8.65 (s, 1H, CH¼N–Ar); 7.50–6.70
(Ar–H), 4.90 (s, 2H, CH2), 3.83–3.74 (d, 3H, OCH3). 13C-NMR (CDCl3 as solvent, ꢂ in
ppm): 163 (C-7), 162 (C-15), 161.5 (C-1), 151.5 (C-14), 151.0 (C-17), 149.5 (C-18), 133.0
(C-3), 132.0 (C-5), 129.5 (C-9), 128.5 (C-10), 127.2 (C-11), 127.1 (C-12), 124.2 (C-6),
123.8 (C-22), 119.0 (C-4), 118.5 (C-13), 117.2 (C-16), 117.0 (C-2), 116.0 (C-21), 115.0
(C-20), 61 (C-8), and 56 (C-19).
2.4. Synthesis of CuL
Cu(II) acetate (4 mmol) was dissolved in 20 cm3 methanol and added dropwise
to a stirred warm solution of the ligand (4 mmol) in 20 cm3 methanol. The resulting
solution was stirred for 2 h. The solid was first filtered, then washed with methanol and
diethyl ether, and finally dried in vacuum (figure 3).
CuL: Yield (50%), color: green, m.p. 4250ꢁC. ꢃeff: 1.78 BM. (C22H18CuN2O3) Found
% (Calcd %): C: 62.59 (62.62), H: 4.36 (4.30), N: 6.62 (6.64), Cu: 15.10 (15.06).

Schiff-base electropolymer
2185
IR (KBr, cmꢀ1): 3050 ꢀ(Ar–H), 2828 v(CH2), 1611; 1599 ꢀ(CH¼N), 1244; 1214 ꢀ(C–O),
543 ꢀ(Cu–O) and 485 cmꢀ1 ꢀ(Cu–N). UV-Vis (ꢁmax, nm, MeOH): 286, 388, 423
(as a shoulder), and 620.
2.5. Electropolymerization procedure of CuL
Electrochemical synthesis of the polymeric film was carried out using CV [16].
Poly[CuL] film was deposited by cycling the potential of the working electrode between
0.0 and 1.6 V at 100 mV sꢀ1 in 10 polymerization cycles, immersed in an acetonitrile
(CH3CN) solution containing 5 mmol dmꢀ3 of CuL and 0.1 mol dmꢀ3 lithium
perchlarate (LiClO4) under nitrogen. After polymerization, the modified electrode
was first rinsed with CH3CN and then twice with distilled water.
3. Results and discussion
The elemental analyses are in good agreement with the suggested compositions of the
ligand and its metal complex. The ligand is formed in nearly quantitative yield. The
yield of the complex is lower perhaps due to steric hindrance around the coordination
center [22]. The ligand and its metal complex are soluble in common organic solvents
such as MeOH, CH3CN, and THF.
Magnetic measurement of the complex was recorded at room temperature and the
effective magnetic moment (ꢃeff) was 1.78 BM, confirming tetrahedral geometry [19, 23].
A similar complex [Cu(salabza)] prepared from the Schiff base from 2-aminobenzyla-
mine, also has tetrahedral geometry [23]. Elemental analysis (CuL) supports the
tetrahedral geometry of [CuL] in this study.
Mass spectra of H3A and H2L show peaks at m/e 227 and 361, respectively,
attributed to the molecular ion peaks [M]þ.
Electronic spectra of H3A, H2L, and [CuL] have been measured in EtOH. The
aromatic bands of the compounds in the 270–286 nm range are attributed to benzene
ꢄ–ꢄ* transitions. Bands in the 320–423 nm range are assigned to imine n–ꢄ* transitions.
In the spectrum of the complex, bands of the azomethine ꢄ–ꢄ* transition are shifted
to lower frequencies indicating that the imine nitrogen is involved in the coordination
to copper [21]. In addition, the band observed at 620 nm can be assigned to d–d
transition of the metal ion [19, 24].
3.1. FT-IR spectra
FT-IR spectral data are given in table S1 in ‘‘Supplementary material.’’ In the spectrum
of H3A, bands at 3374–3221 cmꢀ1 can be attributed to primary amine vibrations.
Therefore, the presence of primary amine group in H3A prove the mono condensation
of 2-aminobenzylamine with salicylaldehyde. The single sharp peak at 1630 cmꢀ1
assigned to the CH¼N vibration also indicates mono condensation. Disappearance of
bands at 3374–3221 cmꢀ1 and the presence of a new band at 1615 cmꢀ1 (for CH¼N) in
the spectrum of H2L proves the condensation of aldehyde of 3-methoxysalicylaldeheyde
with amine of H3A. H2L has two different azomethine groups, Ar–N¼CH– and
–CH2–N¼CH–, observed at 1615 and 1630 cmꢀ1, respectively [25, 26].

2186
C. Demetgul et al.
¨
In the spectrum of Cu(II) complex of H2L, the O–H modes are no longer observed,
denoting that protons are displaced by the metal ion leading to M–O bonding.
In addition, the CH¼N bands of H2L shift from 1630 and 1615 cmꢀ1 to 1611 and
1599 cmꢀ1 after complex formation because of the involvement of nitrogen
in coordination [2, 27]. New peaks were observed with low intensity in the FT-IR
spectrum of Cu(II) complex at 543 and 485 cmꢀ1 assigned to metal–O and metal–N
stretching, respectively [27, 28].
For all compounds weak bands observed at 2878–2834 cmꢀ1 are assigned to –CH2–
group vibration. The FT-IR spectra of compounds are provided in ‘‘Supplementary
material.’’
3.2. 1H- and 13C-NMR spectra
The 1H- and 13C-NMR spectra of H3A were recorded in CDCl3 and the spectra of H2L
in DMSO-d6 and CDCl3, respectively. The 1H- and 13C-NMR spectral data of H3A and
1
H2L are given in table S2 in ‘‘Supplementary material’’. In the H-NMR spectrum of
H3A, singlets at 8.60 and 3.70 ppm can be attributed to CH¼N and NH2, respectively.
The singlet at 13.15 ppm is assigned to OH proton of H3A, whereas broad signals in the
13.60–13.00 ppm range are attributed to OH protons, due to different phenolic moieties
in the structure of H2L. A new resonance at 3.83–3.74 ppm may be assigned to methoxy.
There are two different azomethine groups –CH2–N¼CH– and Ar–N¼CH–. The
proton of the first is at 8.65 ppm and the other 8.90 ppm, for the ligand [26]. Multiplets
in the 7.50–6.70 ppm range can be attributed to protons of benzene rings of both H3A
and H2L. Also, the –CH2– protons of these compounds are observed at 4.70–4.90 ppm.
1
The H-NMR spectra of H3A and H2L are provided in ‘‘Supplementary material’’.
More detailed information about the structures of the new Schiff bases (H3A and
H2L) is provided by the 13C-NMR spectral data, which confirm the results of the
1H-NMR spectra. The carbons of CH¼N–CH2– are at 163 and 59 ppm, respectively
[26]. In the 13C-NMR spectrum of H2L, two new signals at 162 and 56 ppm are assigned
to CH¼N and OCH3 carbons, respectively. Carbons of benzene rings are observed
at 161.6–115 ppm.
3.3. Electrochemical characterization of the monomer
Cyclic voltammograms of CuL are shown in figure 4 for different solvent media.
In acetonitrile þ LiClO4 on the positive scan, one well-defined oxidation peak and two
reduction peaks are found, whereas in dichloromethane þ LiClO4 no peak can be
observed. Therefore, the electrochemical data obtained in acetonitrile of the complex
using LiClO4 as a supporting electrolyte are collected.
The ratio of cathodic to anodic peak currents at various scan rates was almost unity
(figure 5). The reduction and oxidation peak currents for entrapped Cu2þ/Cu3þ linearly
increase with potential scan rates between 5 and 200 mV sꢀ1 (figure 5). Linear
correlation of the peak current with scan rate shows that the system is similar to
a surface-controlled process. These results suggest that all the electroactive Cu(II) in the
film has been converted in Cu(III) during the reverse scan. Additionally, the difference
in potential between the anodic peak and the cathodic peak was practically constant
over the range of scan rates; such behavior may be due to a good interaction between
the electrode and the site of activation of the polymer (metallic cation) [29].

Schiff-base electropolymer
2187
Figure 4. CV of [CuL] monomer (ca 5 mmol dmꢀ3
)
in dichloromethane þ LiClO4 (a) and in
acetonitrile þ LiClO4 (b) on Pt at scan rate 100 mV sꢀ1. Potentials are referred to Ag/Agþ.
Figure 5. CV of [CuL] (ca 5 mmol dmꢀ3) in acetonitrile þ LiClO4 on Pt sheet electrode at various scan
rates (mV sꢀ1): (a) 5; (b) 10; (c) 20; (d) 30; (e) 50; (f) 80; (g) 100; (h) 150; and (i) 200. Potentials are referred
to Ag/Agþ.
The peak current changes linearly with scan rate (ꢀ) according to equation Ip ¼ Aꢀx.
The x values 1.0 and 0.5 are expected for adsorption and diffusion controlled reaction,
respectively. For 5 mmol dmꢀ3 [CuL] monomer, the regression of log(Ip) versus log(ꢀ)
gave a slope of 0.4 (figure 6), indicating that the reduction current had contributions
from diffusion current [30, 31].
3.4. Electropolymerization of CuL
Cyclic voltammograms in 0.1 mol dmꢀ3 LiClO4/CH3CN of CuL are very similar to those
observed for solutions of nickel complexes with the same ligands (figure 7) [15, 16].
They are typical of irreversible systems, showing a continuous increase in current
intensity with the number of scan cycles, reflecting the accumulative electrosynthesis
of an electroactive polymer.

2188
C. Demetgul et al.
¨
Figure 6. Logarithm of anodic peak current as a function of logarithm of scan rate in the range
5–700 mV sꢀ1
.
Figure 7. Series of sequential cyclic voltammograms for anodic polymerization of 1 mmol dmꢀ3 [CuL]/
0.1 mol dmꢀ3 LiClO4/CH3CN at a Pt sheet electrode, between 0.0 and 1.6 V for 12 polymerization scans
(ꢀ ¼ 0.100 V sꢀ1).
The first scan is different from the subsequent ones and shows one well-defined
anodic peak at 1.21 V, and the cathodic process consists of low intensity wave at 0.73 V
for CuL. After the first cycle, a new anodic broad peak appears at ca 0.83 V. Together
with the wave at 0.73 V, they grow continuously with the number of polymerization
cycles. For poly[CuL], the peak at 0.73 V shifts slightly toward more negative potential,
and the new peak at 0.83 V shifts slightly toward more positive potential after each
consecutive cycle.
Peak current intensities at ꢀ ¼ 0.1 V sꢀ1 during polymerization cease to increase after
about 12 polymerization scans for poly[CuL], and then slowly start to decrease. Visual
inspection of the working electrode after cycling in monomer solution shows a green
insoluble film on the Pt surface (Supplementary material).
Consecutively increasing currents for both anodic and cathodic peaks demonstrate
that [CuL] films are continuously deposited on the electrode surface with increasing

Schiff-base electropolymer
2189
(a)
(b)
N
N
Cu2+
O
N
N
O
2+
Cu
OO
N
N
2+
Cu
N
N
2+
Cu
H3CO
OO
OO
N
N
2+
Cu
H3CO
H3CO
H3CO
OO
N
N
2+
Cu
N
N
2+
Cu
H3CO
OO
N
N
OO
2+
Cu
H3CO
OO
N
H3CO
N
2+
Cu
N
N
2+
Cu
H3CO
OO
N
N
2+
OO
Cu
OO
N
N
H3CO
2+
N
N
H3CO
2+
Cu
OO
Cu2+
O
N
N
H3CO
Cu
OO
H3CO
N
H3CO
O
N
2+
Cu
OO
N
N
N
N
2+
2+
Cu
OO
Cu
N
N
2+
H3CO
Cu
OO
OO
N
N
2+
Cu
N
N
2+
Cu
H3CO
H3CO
OO
H3CO
H3CO
OO
H3CO
N
N
2+
Cu
H3CO
OO
N
N
2+
Cu
N
N
2+
Cu
H3CO
OO
OO
N
H3CO
N
H3CO
Cu2+
O
Platinum electrode
O
H3CO
Figure 8. Scheme of electropolymerization mechanism of [CuL] on platinum electrode (a) and platinum
electrode modified by nanostructured poly-[CuL] film (b).
number of potential scans. In each successive cycle of polymerization of the complex,
the cathodic/anodic peaks (0.73 and 0.83 V vs. Ag/Agþ) corresponding to the redox
process between Cu2þ and Cu3þ shifted for more positive potentials. The mechanism
of the electrooxidative polymerization of the copper complex still remains unclear.
However, according to previously reported data on the anodic oxidation of metal salen
complexes [18], the polymerization occurs for a potential peak of about 1.09 V versus
saturated calomel electrode (SCE), which corresponds to electron transfer from
predominantly ligand-centered orbitals [32]. Visual inspection of the electrode surface
showed the deposition of a green film; as this film was not dissolved upon subsequent
anodic or cathodic scans, we have concluded that the product of oxidation of [CuL]
is also a polymeric material (figure 8) [18].
Electrochemistry of the poly[CuL]-Pt and bare Pt in 0.1 mol dmꢀ3 LiClO4/CH3CN
are shown in figure 9. The surface CVs of the poly[CuL] films, carried out in a
monomer-free acetonitrile þ 0.1 mol Lꢀ1 LiClO4 solution, demonstrate that the depos-
ited film at the surface has one anodic and one cathodic peak, although bare Pt
electrode is electroinactive, from 0 to þ2.0 V. This implies that the film is electroactive
against positive scans up to 2.0 V.
The method of Sharp et al. [33] was used to roughly estimate the surface
coverage of the electrode by background-corrected electric charge (Q). According
to this method, the relation between the peak current and the surface coverage
is given as
n2F2Aꢀv
Ipa
¼
ð1Þ
4RT

2190
C. Demetgul et al.
¨
Figure 9. Cyclic voltammograms of bare Pt electrode and poly[CuL] on Pt electrode as working electrode in
0.1 mol dmꢀ3 LiClO4/CH3CN. Potentials are referred to Ag/Agþ.
where n represents the number of electrons involved in the redox pair, A is the area
of the electrode (0.2 cm2), ꢀ is the surface coverage (mol cmꢀ2), ꢀ is the scan rate (V sꢀ1),
and R is the gas constant (8.314 VCKꢀ1 molꢀ1); and other symbols have their usual
significance. The calculated surface coverage is based on depositions carried out with
three separate electrodes and the values are not very much different from each other.
The average surface coverage was found to be 4.6 ꢂ 10ꢀ9 mol cmꢀ2. To obtain an ultra
thin membrane bound to the electrode surface, 12 cycles of potential scans were
performed during the electropolymerization.
4. Conclusion
Synthesis and characterization of a new Schiff base and its complex with Cu(II) suggest
that the tetradentate ligand coordinates to Cu(II) through the phenolic oxygen and
azomethine nitrogen. Use of this metal complex in the preparation of a modified
electrode is also described. The unsymmetrical Cu(II) complex was electropolymerized
on a platinum electrode surface and electrochemical properties of this nanostructured
polymeric film have been investigated. In view of its stability, low working potential,
simplicity, and low cost of construction, the polymer [CuL] film shows promising
characteristics for investigation as sensor for the analysis of real samples, containing fine
particles, deep color, or high viscosity. This new electrode may find application in
catalytic reduction and oxidation reactions due to the unsymmetrical geometry of [CuL].
Acknowledgments
The authors are grateful to the Science Research Fund of the C¸ ukurova University in
Turkey for supporting this study (project no. FEF2009YL-3) and to the Department of
Chemistry of Mustafa Kemal University for allowing the use of its laboratory facilities.

Schiff-base electropolymer
2191
References
[1] R.H. Holm, G.W. Everett, A. Chakravorty. Prog. Inorg. Chem., 7, 83 (1966).
[2] M. Tumer, H. Koksal, S. Serin. Transition Met. Chem., 24, 13 (1999).
¨
¨
[3] A.D. Garnovskii, I.S. Vasilchenko, D.A. Garnovskii, B.I. Kharisov. J. Coord. Chem., 62, 151 (2009).
[4] Z.L. You, H.L. Zhu. Anorg. Allg. Chem., 630, 2754 (2004).
[5] A. Golcu, M. Tumer, H. Demirelli, R.A. Wheatley. Inorg. Chim. Acta, 358, 1785 (2005).
¨
¨
¨
[6] M. Tumer, H. Koksal, M.K. Sener, S. Serin. Transition Met. Chem., 24, 414 (1999).
¨
¨
[7] E.G. Samsel, K. Srinivasan, J. Kochi. J. Am. Chem. Soc., 107, 7606 (1985).
[8] M. Shamsipur, A.R. Ghiasvand, H. Sharghi, H. Naeimi. Anal. Chim. Acta, 408, 271 (2000).
[9] J. Satio, M. Mitani, S. Matsui, J. Mohri, S. Kojoh, N. Kashiwa, T. Fujita. Angew. Chem. Int. Ed., 40,
2918 (2001).
[10] R.K. O’Reilly, V.C. Gibson, A.J.P. White, D.J. Williams. J. Am. Chem. Soc., 125, 450 (2003).
[11] M. Shamsipur, S. Sadeghi, H. Naeimi, H. Sharghi. Polish J. Chem., 74, 231 (2000).
[12] A.R. Khorrami, H. Naeimi, A.R. Fakhari. Talanta, 64, 13 (2004).
[13] R.P. Kingsborough, T.M. Swager. In Progress in Inorganic Chemistry, K.D. Karlin (Ed.), Vol. 48,
pp. 123–231, Wiley, New York (1999).
[14] C.E. Dahm, D.G. Peters. J. Electroanal. Chem., 406, 119 (1996).
[15] M. Vilas-Boas, C. Freire, B. Castro, A.R. Hillman. J. Phys. Chem., B102, 8533 (1998).
[16] M. Martins, M. Vilas-Boas, B. Castro, A.R. Hillmanan, C. Freire. Electrochim. Acta, 51, 304 (2005).
[17] L. Mao, K. Yamamoto, W. Zhou, L. Jin. Electroanalysis, 12, 72 (2000).
[18] T.R.L. Dadamos, M.F.S. Teixeira. Electrochim. Acta, 54, 4552 (2009).
[19] M. Tumer, D. Ekinci, F. Tumer, A. Bulut. Spectrochim. Acta, Part A, 67, 916 (2007).
¨
¨
[20] D.M. Boghaei, M. Lashanizadegan. Synth. React. Inorg. Met.-Org. Chem., 30, 1393 (2000).
[21] C. Celik, M. Tumer, S. Serin. Synth. React. Inorg. Met.-Org. Chem., 32, 1839 (2002).
[22] M. Tumer, B. Erdog
¸
¨
˘
an, S. Serin, M.Y. Nutku. Synth. React. Inorg. Met.-Org. Chem., 28, 529 (1998).
¨
[23] M. Sasaki, K. Manseki, H. Horiuchi, M. Kumagai, M. Sakamoto, H. Sakiyama, Y. Nishida, M. Sakai,
Y. Sadaoka, M. Ohba, H. Okawa. J. Chem. Soc., Dalton Trans., 259 (2000).
[24] P.S. Subramanian, E. Suresh, P. Dastidar. Polyhedron, 23, 2515 (2004).
[25] M. Vazquez, M.R. Bermejo, M. Fondo, A.M. Garcia-Deibe, J. Sanmartin, R. Pedrido, L. Sorace,
D. Gatteschi. Eur. J. Inorg. Chem., 1128 (2003).
[26] C. Demetgul, M. Karakaplan, S. Serin, M. Dig
˘
rak. J. Coord. Chem., 62, 3544 (2009).
[27] C. Demetgul, M. Karakaplan, S. Serin. Des. Monomers Polym., 11, 565 (2008).
¨
¨
[28] H. Koksal, M. Dolaz, M. Tumer, S. Serin. Synth. React. Inorg. Met.-Org. Chem., 31, 1141 (1997).
¨
¨
[29] A.J. Bard, L.R. Faulkner. Electrochemical Methods: Fundamentals and Applications, 2nd Edn, Wiley,
New York (2001).
[30] A. Sevcik. Czech. Chem. Commun., 20, 327 (1948).
[31] N. Menek, Y. Karaman. Dyes Pigm., 68, 101 (2006).
[32] S.V. Vasil’eva, I.A. Chepurnaya, S.A. Logvinov, P.V. Gaman’kov, A.M. Timonov. Russ. J. Electrochem.,
39, 310 (2003).
[33] M. Sharp, M. Petersson, K. Edstrom. J. Electroanal. Chem., 95, 123 (1979).